1. Field of the Invention
The present invention relates in general to an apparatus and method for determining a washing pattern according to the type of a material of laundry, and more particularly to a washing pattern determination apparatus and method wherein a microcomputer judges the type of a material of laundry put into a washing tube of a direct drive-type washing machine on the basis of a voltage variation measured through resistors in a voltage variation sensing device when a motor is driven, as well as the amount of the laundry, and then varies a washing pattern appropriately to the judged laundry material type.
2. Description of the Prior Art
Generally, if laundry such as dirty clothing is put into washing liquid within a washing tub of a washing machine, then it is removed of dirt owing to a chemical action of a detergent. But, because a large amount of time is required in washing off the dirt from the laundry with only the chemical action of the detergent, a mechanical action such as friction or vibration is additionally applied to the laundry to increase the washing speed of the laundry.
A conventional method for controlling a washing mode of such a washing machine comprises sensing and judging the amount of laundry, such as clothing, put into a washing tub, setting the flow of water, the type of a detergent and the total washing time according to the judged laundry amount, agitating the water by normal and reverse rotations of an agitator for the set washing time and separating dirt from the laundry by its friction with the water.
In the above-mentioned washing mode control method, in order to maintain the level and flow pattern of water appropriate to the amount of laundry in the washing tub at the initial step of the washing mode, a water supply valve is opened to a degree depending on the laundry amount and then supplies water up to a set level. Typically, a laundry amount sensing device is adapted to sense the amount of laundry in the washing tub.
FIG. 1 shows the construction of a conventional laundry amount sensing device for a washing machine. As shown in this drawing, the conventional laundry amount sensing device comprises a voltage converter 10 for inputting an external alternating current (AC) voltage and rectifying and smoothing the inputted AC voltage to convert it into a direct current (DC) voltage, a switch 11 for performing a switching operation to transfer motor drive signal current, a motor 12 rotating in response to the motor drive signal current from the switch 11 to perform a driving operation, and a microcomputer 13 for generating the motor drive signal current, sensing the driving operation of the motor 12 and controlling a washing pattern based on the amount of laundry in accordance with the sensed result.
A hall sensor 14 is attached to the motor 12 to sense the number of revolutions and rotation velocity of the motor 12.
FIG. 2a is a graph showing a waveform of an output signal from the hall sensor 14 when laundry is light, and FIG. 2b is a graph showing a waveform of an output signal from the hall sensor 14 when laundry is heavy.
A description will be given of the operation of the conventional laundry amount sensing device with the above-mentioned construction with reference to the drawings. If a washing mode of the washing machine is started, the microcomputer 13 drives the motor 12 in a laundry amount sensing pattern to rotate a washing tub under the condition that no wash water is supplied to the washing tub. Thereafter, if the microcomputer 13 turns off the drive signal to the motor 12 as indicated by D and F in FIGS. 2a and 2b, then the motor 12 makes surplus rotations owing to inertia.
While the motor 12 makes surplus rotations in this manner, the hall sensor 14 attached to the motor 12 generates signals having different surplus rotational periods and times according to different amounts of laundry, by E and G in FIGS. 2a and 2b. 
The microcomputer 13 processes such output signals from the hall sensor 14 as interrupt signals, judges the amount of laundry from a difference between their numbers, sets a washing pattern, such as a washing speed or time, on the basis of the judged laundry amount and performs the washing mode according to the set washing pattern.
FIG. 3 is a graph showing the number of surplus revolutions of the motor 12 depending on the amounts of laundry. It can be seen from this drawing that the number of the surplus revolutions of the motor 12 increases as laundry becomes heavier.
However, the above-mentioned conventional washing machine has a disadvantage in that the washing pattern is set on the basis of only the sensed laundry amount irrespective of the kind of the laundry put into the washing tub. In other words, if the laundry is thin and light, it may be damaged due to over-washing. On the contrary, in the case where the laundry is thick, it may be poorly washed.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide washing pattern determination apparatus and method wherein a microcomputer judges the type of a material of laundry put into a washing tub of a washing machine on the basis of a voltage variation resulting from its friction with water when a motor is driven, as well as the amount of the laundry, and then varies a washing pattern appropriately to the judged laundry material type.
In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a washing pattern determination apparatus comprising a voltage converter for inputting an external alternating current (AC) voltage and rectifying and smoothing the inputted AC voltage to convert it into a drive voltage necessary to a washing mode of a washing machine; a switch for performing a switching operation in response to a motor drive control signal to transfer the drive voltage from the voltage converter to a motor so as to rotate or stop a washing tub; voltage variation sensing means for measuring a voltage variation when the motor rotates in response to the drive voltage transferred from the switch and outputting the measured result as a voltage variation sense signal; and a microcomputer for driving the motor in a laundry amount sensing pattern at the time that laundry is put into the washing tub, judging the amount of the laundry and the amount of water supply depending on the laundry amount, judging the type of a material of the laundry in response to the voltage variation sense signal from the voltage variation sensing means at the time that wash water is supplied to the washing tub, producing an optimum washing pattern appropriate to the amount and material type of the laundry within the washing tub and generating the motor drive control signal to drive the motor in the produced optimum washing pattern.
Preferably, the voltage variation sensing means may include a pair of sensing resistors connected to a direct current (DC) link terminal connected to a switch performing a switching operation to drive the motor.
In accordance with another aspect of the present invention, there is provided a washing pattern determination method comprising the steps of a) driving a motor in a laundry amount sensing pattern if laundry is put into a washing tub and judging the amount of the laundry and the amount of water supply depending on the laundry amount; b}supplying wash water to the washing tub if the step a) is completed, driving the motor in a laundry material sensing pattern, measuring a voltage variation applied across a DC link terminal connected to a switch performing a switching operation to drive the motor and generating a voltage variation sense signal in accordance with the measured result; c) judging the type of a material of the laundry in response to the voltage variation sense signal generated at the step b) and producing a washing pattern appropriate to the amount and material type of the laundry within the washing tub; and d) generating a motor drive control signal to drive the motor in the washing pattern produced at the step c), thereby performing an optimum washing mode.